An ordinary water bottle cap will fit any Platypus bottle https://www.platy.com/bottles-storage (by the wonderful Cascade Designs who also make the absolutely best Sleeping Pad: https://www.thermarest.com/mattresses/womens-neoair-xlite).
You can make holes with a large needle (doll needle pictured – much safer). With nine holes as pictured one litre lasts 6 ½ minutes. I usually carry one 2 litre Platypus and a one litre one. Della carries the same. Similarly each has a pot of approx one litre capacity. A litre of boiling water added to a litre of cold water makes a pretty good shower temperature. 4 litres of water each gets us pretty clean in the backcountry where there is plenty of wood to provide the heat, eg with this: http://www.theultralighthiker.com/the-egg-ring-ultralight-wood-burner-stove/
A couple of grommets in the base of the Platypus bottle (both on one side) will allow you to hang it up from a carabiner on a piece of string. A loop tied with an overhand knot in the string a little higher up will allow you to catch the neck of the bottle to turn the shower off. I am working on converting one of those water bottle on/off bite valves which some water bottles come with to a shower for the same purpose. Looking for a cap which can be glued on which is just the right size, but really it works just fine as above.
Like this (7 grams):
Keeping your clothes clean is important too: http://www.theultralighthiker.com/ultralight-clothes-pegs-for-hiking/
There are a variety of purchasable models of this device (some very dear) and all of which weigh more than a gram! Make your own and convert your Platypus bottles for hanging (2 minutes max)
http://www.theseedbomblaboratory.com/bottle-top-sprinklers.html http://www.ebay.com/itm/WATERING-CAP-ATTACH-SOFT-DRINK-BOTTLE-PLANT-MINI-SPRINKLER-SHOWER-PLASTIC-x6-PC-/161933729804?hash=item25b400a00c:g:znkAAOSwK7FWhMc2 http://www.bottleshower.com/about/